酵母菌药用乳糖酶制备新方法

目的:建立一种简易的从酵母菌制备克鲁维酵母乳糖酶的方法.方法:在30L发酵罐中进行发酵,用对羟基苯甲酸酯进行细胞破壁,用超微过滤方法浓缩破壁液.结果:乳糖酶的收率可达到每毫升发酵液含11.4 ONPG单位.从酵终细胞中释放乳糖酶可达70%,每毫升牛奶中加入1.2 ONPG单位制备的液态乳糖酶可使牛奶中的乳糖水解率达到70%.     

Acute renal rejection versus acute tubular necrosis in a canine model: MR evaluation

Findings of magnetic resonance (MR) imaging in acute renal rejection and acute tubular necrosis (ATN) were studied in dogs. On T1-weighted images, corticomedullary differentiation was absent in kidneys undergoing acute rejection. The loss of corticomedullary differentiation in these kidneys was secondary to a decrease in the relative signal intensity of the cortex, indicating prolongation of the T1 relaxation time of the cortex. In contrast, corticomedullary differentiation was preserved on T1-weighted images of autotransplanted kidneys and kidneys with ATN. MR imaging findings correlated with changes in water content in these three groups of kidneys. Kidneys undergoing acute rejection showed a marked increase in water content compared with kidneys in the other two groups. No change in fat content was found in any group.     

The spatial distribution of the antagonistic surround of MT/V5 neurons

The majority (217/325, 66%) of the neurons in the middle temporal (MT) area/V5 show strong antagonistic surrounds, defined here by a decrease of at least 50% in the summation curve. We mapped the antagonistic surround in 145 such cells, using eight circularly distributed surround stimulus patches (Surround Asymmetry Test, SAT) and also mapped the surround in 51 of these 145 cells using a grid consisting of 25 square patches (Surround Mapping Test, SMT). Both tests showed that the angular surround distribution was non-uniform in the majority of these neurons. In half the neurons, the antagonistic surround was asymmetric, and arose from a single region on one side of the excitatory receptive field (ERF). In another quarter of the sample the surround was bilaterally symmetric, and arose from a pair of regions on opposite sides of the ERF. Only the remaining 20% showed a circularly symmetric surround distribution. These three groups differed in their laminar distribution. The SMT showed that, radially, the surround antagonism reached a maximum, on average, at 1.5 times the ERF radius. Detailed comparisons of the spatial relationships of excitatory and inhibitory regions of the RF components shows that non-homogeneity of the surround influence appears to be an intrinsic property of the surround. Such a property may underly the extraction of the surface orientation and curvature from speed patterns.